Undertake any work when the tree is most dormant – i.e. mid winter. However, reducing the size of a pohutukawa is not easy. If you cut large branches back you will precipitate epicormic growth back along the remaining branch which thickens up the within tree foliage. In shaping pohutukawa we aim to retain the umbrella shaped outer canopy while lifting the crown and creating a view beneath it. You end up looking through the stems beneath the crown, so you don’t want epicormic growth.
It is important to keep a balanced crown so if any large branches are to be removed it should be done right back at the trunk, but not so that it leaves a lopsided or large gaps in the crown. A bit tricky, it is difficult to retain the overall shape of the tree when removing major branches.